Surgical procedures have historically utilized the application of electrical cautery to stop bleeding at the surgical incision as well as lower energy electrical pulses for nerve stimulation to locate nerves adjacent the surgical site. Electrically conductive instruments are touched to tissue at the surgical site, these instruments being attached to an electro-cautery power source or a nerve stimulation pulse generator.
An insulated conductive suction device has been found useful for application of electrical energy to human patients for cautery. U.S. Pat. No. 6,947,098 shows an electrical cautery with a ball point roller like tip. It includes a central lumen for delivering a fluid to openings near the roller ball tip. While it does not include a suction channel for removal of the fluid or smoke from the tissue ablation procedure, it is indicated that suction channels shown in other patents, such as U.S. Pat. No. 5,269,781, can be added. US RE 40,156 is an example of an electric ablation device for destroying intervertebral discs. The device may also include lumens for delivering fluids to wash away debris created by the ablation and a suction channel for removing the fluid and debris. However, such a device would not be suitable for nerve stimulation along the walls of a hole drilled in the pedicle to locate adjacent nerves. Often the energy source wire is merely clipped to the instrument. Inclusion of a terminal for attachment of the stimulating or cautery lead wire more permanently to the instrument provides a more reliably and quantitatively verified delivery of the electrical energy.
U.S. Pat. No. 5,775,331 describes a device for electrical stimulation to locate a nerve and also indicates the device may include a suction channel for removing fluids. A major problem of present designs of suction cauterys or nerve stimulators with suction capability is that the lumen of the suction device can become repeatedly blocked and clogged by bone chips or tissue when applied to a freshly drilled hole in bone. In addition, the open tip of the presently available open-end suction tube designs poses a risk of trauma to fragile nervous and vascular structures from the direct application of suction.
Under certain circumstances a medically desirable procedure is the stabilization or fusion of a portion of the spine to prevent motion. For example, the spine may be stabilized after a decompression procedure where certain posterior spinal elements are removed to relieve pressure on nerves within the spine. It may also be necessary to stabilize or fuse the spine following trauma or the removal of tumors. As part of those procedures pedicle screws are inserted in selected vertebrae to hold stiff rods or plates between adjacent pedicles, resulting in the fixing or bracing of all vertebrae spanned by the rod or plate. The pedicle screws are usually made of stainless steel and typically have thread outer diameters from about 5.5 mm to about 6.5 mm, and lengths between about 25 mm to 55 mm. One of the major causes of unsuccessful back surgery is the proximity of the screw to one or more nerves within the spine or pedicle creating chronic pain.
Because the pedicles are the strongest parts of the spinal vertebrae this arrangement provides a secure foundation for the attached rods or plates. However, maximum mechanical integrity is obtained when the anchoring pedicle screws are threaded in alignment with the pedicle axis. If they are allowed to deviate off axis the screw body or its threads can break through the vertebral cortex and impinge on or become dangerously close to surrounding nerve roots. Slight deviations in the angle of screw insertion can injure the nerve roots or the spinal cord. Even if the pedicle screw is properly aligned it may be placed to close to a nerve, resulting in chronic, postoperative pain. There are numerous articles in the literature regarding the problems of misalignment of pedicle screws and the symptoms arising when the screws make contact with neural elements after breaking outside the pedicle cortex. Cutting into a nerve root or simply contacting the root gives rise to various postoperative symptoms such as dropped foot, neurological lesions, sensory deficits, or pain. (The Adult Spine—Principles and Practice, Vol. II, at pages 1937 and 2035-36 (Raven Press 1991); J. L. West, et al, Complications of the Variable Screw Plate Pedicle Screw Fixation, Spine (May 1991), at pages 576-79; and J. L. West, et al, Results of Spinal Arthrodesis with Pedicle Screw-Plate Fixation, Journal of Bone and Joint Surgery (September 1991), at pages 1182-83.)
While there are various disclosures of devices designed to properly align the screws, no tools or devices are known with which pedicle screws can be guided or inserted into a vertebra in such a manner as to ensure that the screws do not come unnecessarily close to adjacent nerves. The surgeon may use recognized landmarks along the spinal column for purposes of locating pedicle entry points and X-rays or fluoroscopy to monitor the advancement of a metallic pedicle screw through the vertebra. However, prolonged exposure of the patient to X-rays for purposes of proper screw placement is not desirable and this technique can still result in an unacceptable level of pedicle screw placement.
It is also generally known that electrical potential pulses may be applied on or into the body of a patient for purposes of treatment. For example, U.S. Pat. No. 4,461,300 (Jul. 24, 1984) discloses a specially formed electrode for healing of bone or soft tissue fractures in a patient. The electrode has a lead wire connected at its back end, and is capable of being drilled or otherwise inserted into the patient's body with the lead wire in place.
An alternative technique is to monitor muscular response to electrical stimulation during a screw placement procedure or the drilling of a hole to receive the screw. U.S. Pat. No. 2,808,826 shows electro-diagnostic apparatus and associated circuitry that act as a stimulator to measure the excitability of muscle or nerve tissue. A pair of electrodes are placed across a part of the patient's body and short duration pulses are applied with the pulse amplitude being slowly increased until a visible contraction appears. Electrical current readings are obtained for pulses of increasing duration, and a curve called a “strength-duration” curve is obtained.
U.S. Pat. No. 4,824,433 discloses a puncturing and catheterizing device with a metal puncture needle and cannula suitable for puncturing nerve tracts. Pulses of electrical current applied to the device induce visible motor reactions on body parts such as the hand. The visible muscle responses or responses detected by suitable electronic metering devices allow the physician to know if the current delivery electrode is undesirably close to a nerve.
One skilled in the art is familiar with nerve stimulation electrodes and systems such as are typically used in motor nerve location and monitoring procedures performed during various medical procedures such as thyroidectomy, anterior cervical fusion, craniotomy, skull base procedures, carotid endarterectomy. Typical procedures where nerve location is beneficial is EMG nerve location, locating and monitoring the recurrent laryngeal nerve, xth cranial nerve and other nerves using laryngeal surface electrodes and surface electromyography to preserve vocal cord function and prevent vocal cord injury. The technology is typically used by ear, nose and throat doctors (ENT, otolaryngologists), orthopedic surgeons and general surgeons in otologic and neck procedures, particularly in thyroidectomy, parathyroidectomy and paratoidectomy procedures.
U.S. Pat. Nos. 5,196,015 and 5,474,558 to Seth Neubardt describe a technique of inserting a screw member into bone tissue of a patient following the formation of a hole for screw placement. The technique describes the application of an electric potential to the interior surface of the hole while observing the patient for nervous reactions to the electric potential. To do so an electric potential is applied to a drill bit used to form the opening in bone tissue for insertion of a screw member, and the response of adjacent nerves is observed during the hole forming procedure.
U.S. Pat. No. 6,796,985 to Bolger, et al. is another patent directed to a neurostimulator attached to the drilling tool.
As an alternative, the holes are drilled with standard orthopedic instruments, the drilled holes are cleaned of fluid and bone debris, and a needle probe attached to a nerve stimulation device is placed in the hole to determine if there are nerve ends adjacent the walls or terminus of the hole such that a screw inserted in the hole will interact with adjacent nerves to cause post surgical pain. Presently, the suction cleaning of the drilled hole and subsequent nerve location are done using separate suction devices and nerve stimulators. This results in inconsistent results as the hole can fill with blood or other fluids after removal of the suction devices; the detection or measurement of the electrical signal conducted between the stimulator tip and the adjacent nerve can then vary due to the time delay between suctioning the hole and applying the nerve stimulation device, or the amount of fluid within the opening.